Pick-Up of Organic Molecules by Mixed Ar Clusters: A Function of Gas Properties and Composition

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This manuscript explores the trapping characteristics of argon mixed clusters towards organic molecules. Through systematic studies on the effects of gas pressure, mixed components (H₂, He, O₂, N₂O, CO₂, etc.), and heating temperature of organic compounds on the trapping probabilities of adenine, uracil, glycine, and ascorbic acid, innovative results with experimental value have been obtained. The optimal stagnation pressure range for pure argon clusters to trap organic molecules (10-30 bar) has been clarified, revealing a differentiated regulation mechanism of trapping efficiency by different mixed gases. The addition of H₂/D₂ can increase the trapping signal intensity by more than 3 times (optimal H₂ mole fraction 40%-50%), while N₂O/CO₂ concentrations exceeding 3 mol% completely inhibit the trapping effect, and He/O₂ has no significant impact. Meanwhile, through comparative experiments of Ar-H₂ and Ar-D₂ systems, the intrinsic relationship between gas molecular mass, cluster size/shape, core-shell structure, and trapping efficiency has been preliminarily correlated, providing key experimental evidence for the application of clusters as organic molecule carriers. The experimental design of the manuscript is rigorous, with sufficient data support, and the data charts can well support the conclusions drawn. However, the manuscript has the following issues:

 a). Lack of direct characterization of cluster structure, with only indirect inference of cluster size, shape, and core-shell structure based on signal intensity, without verifying these structural characteristics through theoretical calculations (such as DFT, molecular dynamics simulations), making it impossible to quantify the structure-activity relationship between structure and trapping efficiency;

b). Ambiguous explanation of the trapping mechanism, with only hypotheses such as "irregular shape increases binding sites" and "core-shell separation affects molecular adsorption" proposed, without analyzing the nature of the interaction between molecules and clusters through energy calculations (such as solvation energy, surface energy) or kinetic simulations;

 c). No discussion on the differences between experimental results and existing theoretical models, such as no comparison of the applicability deviation of the scaling law of cluster formation in mixed gas systems, nor analysis of the gap between trapping probability and gas dynamics theory predictions;

d). Insufficient regulation of experimental variables, with no investigation of the effects of nozzle size, temperature, and other key parameters on cluster formation and trapping efficiency, and insufficient analysis of the root causes of differences in trapping of different organic molecules (such as molecular polarity, structural differences);

 e). Limitations in data processing, with mass spectrometry detection only covering ions below m/z=1000, unable to characterize larger-sized mixed clusters, and the correction method for background signals not fully demonstrated to be reasonable, which may affect data accuracy.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This paper analyzes selected properties of Ar clusters. The topic is currently quite fashionable and will undoubtedly interest many readers. The article is well-structured and well-written. However, some issues require improvement before acceptance. In particular:

- The information on clusters containing H2, He, Ne, and Ar is discussed too briefly and too generally. The importance of this topic for modern chemistry should be emphasized.

- Why adenine (A), C5H5N5; uracil (U), C4H4N2O2; glycine (G), 83 C2H5NO2; and ascorbic acid (AA), C6H8O6) were used as a source of molecular vapors ?

- Can the graph in Fig.1 be described using a correlation formula? The same question applies to Fig. 2-7.

- Paragraph 4.1 - What justifies these particular temperatures?

- More technical details for MS experiments should be added.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

This manuscript reports the pick-up properties of pure and mixed Ar clusters for different organic compounds, including adenine, uracil, glycine, and ascorbic acid. The effects of gas pressure, cluster composition, and the heating temperature of the compounds were systematically examined. The experimental design is sound, and the conclusions are carefully drawn based on efficient and reliable data analysis. The method is interesting and potentially useful. The manuscript is generally well organized, and several figures are provided. I believe this work meets the high standards of Molecules and will attract broad interest from readers.

However, several issues should be addressed before the manuscript can be considered for acceptance:

1. The limitations of this method should be clarified. What types of organic molecules are suitable for this approach, and which classes of compounds are not applicable?
2. The scalability of this method should be discussed. Can it be extended beyond laboratory-scale experiments, for example to gram- or kilogram-scale applications?
3. For mixed Ar clusters containing reactive species (e.g., N₂O or O₂), is there a possibility of chemical reactions with the organic molecules at high temperatures? In addition, how are the organic molecules dissociated from the mixed Ar clusters after the pick-up process?
4. If a reader wishes to apply this method to selectively pick up a specific organic molecule, are there any general guidelines rules for identifying suitable mixed Ar cluster compositions promptly?
5. It would be better to include a figure in the Introduction to summarize the background of the research, progress, challenges, this work’s key strategy, novelty, and advantages. A long and tedious text description is not reader-friendly.
6. All figures are too simple. A lot of information described in the main text is not shown in the figures. Reading the figures is confusing.
7. Page 2, line 80: “...was Ar, and ..., and CO2 were added...” is ambiguous.
8. Page 2, lines 86–88: “Pick up..., and heating temperature of the organic compound.” is ambiguous and not reader-friendly.

Comments on the Quality of English Language

The English overall is OK, but ambiguities should be avoided.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have revised the manuscript according to all my comments. So I recomend to accept it for publication.